This invention relates to a method of promoting bone growth in a patient.
Adrenomedullin is a 52-amino acid peptide originally identified in a human pheochromocytoma. It has since been found in normal adrenal medulla, as well as other tissues such as the atria, ventricles, endothelial cells, lungs, brain and kidneys. Adrenomedullin also circulates in picomolar concentrations in both rats and man.
Several biological effects have been attributed to adrenomedullin. It has been described as a potent vasodilator, acting directly on the renal, cerebral, mesenteric, pulmonary, and systemic circulations. Administration of adrenomedullin can result in hypotension.
Binding of adrenomedullin to renal tubular membranes has also been observed, and sodium, potassium, and water excretion are increased by adrenomedullin. Adrenomedullin can in addition be a bronchodilator, and it has been reported to modulate the release of pituitary and vasoactive hormones.
The present invention is based on the discovery that adrenomedullin and peptide fragments of adrenomedullin can stimulate proliferation of osteoblasts, which give rise to bone tissue. Accordingly, the invention provides methods for promoting bone growth, and compositions useful for promoting bone growth.
In one aspect the invention provides a method for promoting bone growth in a patient, e.g., a mammal such as a human. The method includes the step of administering a therapeutically effective amount of adrenomedullin or an adrenomedullin agonist to the patient. The patient may be suffering from a disease associated with excessive resorption or breakdown of bone tissue such as osteoporosis or Paget""s disease. The patient may also be suffering from bone losses as a result of immobility, bone fractures, malignancy, endocrine disorders, autoimmune arthritis, or drug use. The patient may also be undergoing a treatment (e.g., corticosteroid treatment, bone marrow transplantation, or oophorectomy) known to result in bone loss.
In another aspect, the invention features a method for prevent or retarding the development of a bone-associated diseases in a subject, e.g. a mammalian subject such as a human. Thus, the adrenomedullin and adrenomedullin agonists described herein may be used, e.g., to prevent development of osteoporosis or Paget""s disease in a subject.
A therapeutically effective amount depends upon the condition being treated, the route of administration chosen, and the specific activity of the compound used and ultimately will be decided by the attending physician or veterinarian. In one embodiment, the adrenomedullin agonist is administered to the patient until the patient""s bone mass has been restored to normal levels. Thus, the duration of the administration may be dependent upon the severity of the patient""s bone loss.
The adrenomedullin or adrenomedullin agonist may be administered parenterally, e.g., administered intravenously, subcutaneously, or by implantation of a sustained release formulation. However, it will be readily appreciated by those skilled in the art that the route, such as intravenous, subcutaneous, intramuscular, intraperitoneal, enterally, transdermally, transmucously, sustained released polymer compositions (e.g., a lactide polymer or copolymer microparticle or implant), profusion, pulmonary (e.g., inhalation), nasal, oral, etc., will vary with the condition being treated and the activity and bioavailability of the adrenomedullin or adrenomedullin agonist being used.
While it is possible for the adrenomedullin or adrenomedullin agonist to be administered as the pure or substantially pure compound, it may also be presented as a pharmaceutical formulation or preparation. The formulations to be used in the present invention, for both humans and animals, comprise any of the adrenomedullin or adrenomedullin agonists to be described below, together with one or more pharmaceutically acceptable carriers thereof, and optionally other therapeutic ingredients.
The carrier must be xe2x80x9cacceptablexe2x80x9d in the sense of being compatible with the active ingredient(s) of the formulation (e.g., capable of stabilizing peptides) and not deleterious to the subject to be treated. Desirably, the formulation should not include oxidizing agents or other substances with which peptides are known to be incompatible. For example, adrenomedullin or adrenomedullin agonists in the cyclized form (e.g., internal cysteine disulfide bond) are oxidized; thus, the presence of reducing agents as excipients could lead to an opening of the cysteine disulfide bridge. On the other hand, highly oxidative conditions can lead to the formation of cysteine sulfoxide and to the oxidation of tryptophane. Consequently, it is important to carefully select the excipient. Ph is another key factor, and it may be necessary to buffer the product under slightly acidic conditions (Ph 5 to 6).
The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing the active ingredient(s) into association with the carrier which constitutes one or more accessory ingredients.
In general, the formulations for tablets or powders are prepared by uniformly and intimately blending the active ingredient with finely divided solid carriers, and then, if necessary, as in the case of tablets, forming the product into the desired shape and size.
Formulations suitable for parenteral (e.g., intravenous) administration, on the other hand, conveniently comprise sterile aqueous solutions of the active ingredient(s). Preferably, the solutions are isotonic with the blood of the subject to be treated. Such formulations may be conveniently prepared by dissolving solid active ingredient(s) in water to produce an aqueous solution, and rendering said solution sterile. The formulation may be presented in unit or multi-dose containers, for example, sealed ampoules or vials.
Formulations suitable for sustained release parenteral administrations (e.g., biodegradable polymer formulations) are also well known in the art. See, e.g., U.S. Pat. Nos. 3,773,919 and 4,767,628 and PCT Publication No. WO 94/15587.
The adrenomedullin or adrenomedullin agonist may also be administered with an bone anti-resorptive agent or another bone anabolic agent. Examples of bone anti-resorptive agents include calcitonin, bisphosphonates (e.g., etidronate, alendronate, or pamidronate), estrogen, and analogs thereof. Examples of bone anabolic agents include parathyroid hormone, parathyroid hormone related protein, cytokines (e.g., TGF-xcex2, IGF-1), growth hormone, and analogs thereof.
In another aspect, the invention features a peptide consisting of between 30 and 26 amino acids and comprising the sequence adrenomedullin(27-52) (SEQ ID NO:1) wherein the carboxyl terminal is a free acid or amidated. Examples of such peptides include adrenomedullin(27-52) (SEQ ID NO:1); adrenomedullin(26-52) (SEQ ID NO:2); adrenomedullin(25-52) (SEQ ID NO:3); adrenomedullin(24-52) (SEQ ID NO:4); or adrenomedullin(23-52) (SEQ ID NO:5) wherein the carboxyl terminal is amidated. Peptides of this invention are described herein, for example, by the following format: adrenomedullin(13-52) (SEQ ID NO:11). The numbers between the parentheses refer to the number of amino acids present in the peptide, e.g., the forty amino acid fragment between the serine residue at position 13 and the amidated tyrosine residue at position 52 of adrenomedullin. The sequence of adrenomedullin is listed in FIG. 1 of European Patent Application No. 622,458 A2.
The invention also includes an adrenomedullin (ADM) agonist 5-25, 6-25 or 7-25 amino acids in length. The ADM agonist comprises a fraction or the entirety of the amino acid sequence ADM(32-40) (SEQ ID NO:14). In some embodiments the ADM agonist is 9-25 amino acids in length and includes the amino acid sequence ADM(32-40) (SEQ ID NO:14), e.g., the ADM agonist can include the amino acid sequences ADM (28-40) (SEQ ID NO:15), ADM(32-52) (SEQ ID NO:16), and ADM (30-52) (SEQ ID NO:17). Other examples of ADM agonists include peptides 10-25, 12-22, or 13-23 amino acids in length and containing the amino acid sequence ADM(32-40) (SEQ ID NO:14).
The ADM agonists described herein are useful in treating diseases for which increased osteoblast proliferation is desirable. Thus, the ADM agonists are useful for treating bone-associated conditions or diseases such as osteoporosis and Paget""s disease and in preventing or inhibiting the development of such bone-associated diseases in subjects at risk for developing these diseases.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments and from the claims.